Study reveals sharks are colour blind

Thursday, 20 September 2012 - 6:41pm IST | Place: Sydney | Agency: IANS
Although sharks are highly visual animals, they world they see lacks colour and will appear as shades of grey like we see when we watch a black and white movie.

New research which could help conserve sharks has confirmed that many of the ocean predators are probably completely colour blind.

The joint study by The Universities of Western Australia (UWA) and Queensland looked at the visual adaptations of two species of wobbegong sharks, which are also known as carpet sharks.

Wobbegongs spend most of their time on the sea floor and hunt mostly at night using an unusual sit-and-wait ambush strategy, the journal The Royal Society's Biology Letters reports.

The original doctoral study by Susan Theiss showed that the wobbegong visual system contains only a single class of cone photoreceptor. Cone photoreceptors are the retinal cells that are used for vision under bright light conditions, whereas rod photoreceptors are used in dim light, according to an UWA statement.

In many animals, more than one type of cone is present in the retina, some of which are sensitive to different parts of the visible spectrum of light. The nervous system can compare these signals to distinguish colours. However, if only one cone type is present, there is no possibility of colour vision.

In the latest study, researchers isolated the genes that encode the cone visual pigment proteins and found that only one cone pigment gene was present.

Research team leader assistant professor Nathan Hart from the UWA Oceans Institute and School of Animal Biology said the study is important to understand how sharks view the world.

"Sharks are highly visual animals, but the world they see lacks colour and will appear as shades of grey like we see when we watch a black and white movie. It may be possible to use this knowledge to change the way a shark reacts to certain objects.

"For example, it may be possible to design long-line fishing lures that are less attractive to sharks to reduce the incidence of shark bycatch. It may also lead to better design of equipment such as wetsuits and surfboards that reduce the risk of shark attack," Hart said.

Hart and the Neuroecology group at UWA led by Shaun Collin, professor, are already developing shark attack mitigation wetsuits.


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